Telephone system



Aug. 17, 1937. F. WOLF I TELEPHONE SYSTEM Filed Jan. 23, 1936 5 Sheets-Sheet l l N! TOR.

FRITZ WOLF .4 'ITORNEY. v

F. WOLF 2,090,171

3 Sheets-Sheet 2 Aug. 17, 1937.

TELEPHONE SYSTEM Filed Jan. 25, 1956 S DR 4 h S 5% Saw I\ g H H fi W E N w S m;

m P .1. h C. NT W 3 :2 I R h ww tmmm. :3 H is; 88 m E 5: :9 N6: N GE Aug. 17, 1937. F. WOLF 2,090,171

TELEPHONE SYSTEM Filed Jan. 23, 1936 3 Sheets-Sheet 3 gQ .Q cs

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I U') D P 1 0 Q JNVENTOR.

N FRITZ WOLF "i E g BY :0 V

\ ATTORNEY.

Patented Aug. 17, 1937 UNITED STATES PATENT OFFICE 2,090,171 TELEPHONE SYSTEM Application January 23 1936, Serial No. 60,415 In Germany January 28, 1935 Claims.

plished by earthing one or other of the leadsof the connecting line which is common to all the traflic directions. In the known arrangel15'. ments of this kind difiiculties are involved in that the earth determining the connecting device to be used in the exchange and hence also the incoming traflic direction operates on subsequently arranged connecting devices and causes unde sired switching operations in these such as toll knock down.

According to the invention the foregoing difficulties are avoided in that switching devices are provided at the junction point connecting the common connecting line with the connecting devices, which, after the connecting path has E been seized, delay the switching through of the speaking line in the particular outgoing traflic direction to be used until after the disconnection from the calling line of the earth which determines the incoming and outgoing traffic direc-' tion.

In order not to have to provide specially equipped connecting devices or special means of access to the groups of connecting devices (by call finders) for this mode of operation which differs from the normal (individual subscribers),

it has already been proposed to arrange special repeaters and junctions before the normal con- 40 necting devices or the approaches thereto, which in dependence upon the characteristic of the incoming traffic direction would set in operation a connecting device corresponding'to this traffic direction for the purpose of establishing the conof the foregoing devices on account of the desirability of avoiding any appreciable modification of the normal connecting device, suoh as the pre-selector or call finder when operating with connecting lines common to several lines or groups of lines. Influencing of the calling and controlling devices has previously only been accomplished by relays connected permanently to the speaking line but this introduces diificulties 55 both in the further establishment of connecting necting path. Difficulties arise in the operation paths and also in the occurrence and transmission of switching operations during the existence of a call. a

The present invention has as one of its objects the arrangement of a connecting path which will allow the calling and controlling devices to be influenced without permitting the devices of the junction to exert any disturbing influence during the final setting up of the call or while the call is in progress, or while it is being released. This is accomplished by providing a relay which characterizes the incoming and outgoing traffic direction and governs the device controlling thejunction, after determining the traflic direction. appropriate tothe call (e. g. after the completion of the pre-selection), the relay is rendered ineffective by a switching means which is placed transitorily under the influence of following switching devices.

a In these systems faultsmay occur in the setting up of a call if, when a call has been initiated by one of the subscribers, the other subscriber happens to take up his receiver before his line has been rendered inoperative. The chance of this happening is small; it is, however, consider- I ably increased if, when setting up such a call, the bell of the station which is not calling is operated through the discharging of the condenser connected with the bell on account of the reversal of the current direction in the one lead of the partyline. Such faults are avoided ac.- cording to the invention in that the reversal of thecurrent direction taking place over the party line is effected in stagesso as to avoid influencing the bell of the station which is not calling before this station is disconnected or locked out.

In the embodiment of the invention the special. line may constitute a so-called two-party line in which a common connecting line is led to a switching point to which the two subscribers are connected. The invention is, however, not limited to an arrangement of this sort. It is easily possible to connect-up more than two subscribers lines at the switching point, or alternatively, instead of subscribers lines, connecting lines, party lines or the like may be connected up.

The drawings comprising Figs. 1, 2, and 3, show by means of the usual circuit diagrams several embodiments and modifications of the various'features of the invention.

In the embodiment of Fig. 1 two subscribers stations TSH and TStZ are shown Whose lines are connected together and to the common connectingline VL at the switching point UStI. This connecting line leads via the switching point UStZ to the exchange devices where an individual pre-selecting device such as ore-selector VWI is provided for each subscriber of the two-party line. Communication between the two subscribers of the party line is not possible.

The mode of operation of Fig. 1 is as follows: If a subscriber, for example the subscriber at station TS'I'I, wishes to set up a call, he takes up his receiver and thereby closes a circuit for relay RI at the switching point UStZ: earth, battery, winding of relay RI, contacts ItI, 2252, a-lead of the" connecting line, winding I of relay UI, contact 2M2, subscribers station TStI, contact 2Iu2, winding II of relay UI, contact3ul, earth. Relay UI in this circuit does not energize. Relay RI energizes, however, and at its contact 4rI closes a circuit for the auxiliary relay HI. This energizes and over its contact 5hI gives the starting impulse to the pre-selector VWI: earth, battery, resistance Wil, contact 5hI, 'b-lead to the pre-seleotor VWI, contact 615, relay R, earth. The pre-selector is set in operation and on leaving the normal position breaks the holding circuit for relay TI which is energized when the system is at normal. Relay TI releases and by opening contact 'ItI breaks the starting circuit for subscriber TStZ and by closing contact 8H prepares the connection of the connecting line to the exchange devices.

When the pre-selector steps to a free group selector relay T in the p-re-selector energizes in the known way and switches the line through to the pre-selector at its contacts 9t and Hit. A circuit is thereby established for Winding II of relay RI the short-circuit for which was removed by the opening of contact I2rl on the energizing of relay RI: earth, battery in the group selector, relay A in the group selector, a-lead, contact 9t, winding II of relay RI, contact IIrI, resistance 40 W22, earth. The winding II of relay RI opposes winding I so that when the former energizes the relay RI, which was previously held energized over resistance Wi3 and contacts I 374 and I ItI, releases. Contacts I2r| and I5r| are thereupon closed and battery from the group selector is thereby connected to the switching point UStI over the a-lead of the connecting-line. At the switching position UStIrelay UI energizes and closes its contact IIiui. After earth has been disconnected from it at the switching point UStI relay UI holds up over earth at the switching point UStZ by way of the circuit: earth, contact I'Irl, resistance Wz', contacts I8hI, 8tI, b-lead of the connecting line, contact IBuI, winding II of relay UI, contact 2Iu2, winding I of relay'UI, a-lead of the pre-selector VW'I, a-lead to the group selector, battery, earth.

As a result of the release of relay'R-I the circuit for relay HI is broken and this relay makes a delayed release on account of its short-circuiting winding. Contact I @hl is accordingly closed after a certain time, while contacts 5M and IBhI are opened. The b-lead is now switched through to the group selector over contact I9hI. This slow acting device ensures that the switching over relay U! at the switching point UStI has duly switched through the Zr-lead of the subscribers line. This prevents the criterion for toll knock down (relay A energized, relay B de-energized) from being given, since potential is connected to the b-lead of the line leading to the pre-selector until the disconnection from earth and the switching through of the b -lead has taken place at the switching over point UStI. The calling subscribers connecting path to the group selector is now established so that dialling can commence. The subsequent operations are the same as those for a normal subscribers connection.

If when starting up a call the pre-selector VWI does not find a free group selector it steps to the IIth contact. Relay R in the pre-selector is accordingly energized again: earth, battery, resistan-ce Wil, contacts 5hI, 6t, relay R, eartln Relay T in the pre-selector energizes over contact 201' and closes its contacts 915 and Hit, so that a circuit is established for winding II of relay RI: earth, battery, resistance WiB, rotary wiper of pre-selector VWI on contact II, contact 9t, winding II of relay RI, contact IIrI, resistance W12, earth. Relay RI releases in the man.- ner already described when subjected to the influence of the opposing winding II and causes the speakingline to be switched through to the preselector in the same manner as when testing on a free group selector. The engaged signal is connected to the 11th step of the pre-selector in the known manner, and is therefore transmitted to the subscriber. The subscriber thereupon replaces his receiver thereby causing the release of the connecting path set up. The pre-selector returns to normal in which position the relay TI at the switching point UStZ again energizes thereby closing contact ItI and HI. The system is now restored to normal. I

. The same operations take place when a call is initiated by the subscriber of the station TSt2 provided that the subscriber of station TSt, is not holding a call at the time. If this is the case the contacts 23ul and 2411.! are open so that the line of the subscriber at station UStZ is doubly disconnected, and manipulation of the switch hook or dial at this station is without effect.

Since however, relay UI or U2 does not energize until the pre-selector has been set in the exchange, devices are provided at the switching point UStZ which prevent the bell at the subscribers station TStZ from operating when the potential on the b-lead of the connecting line, which in the normal condition of the system is negative, is changed to earth potential. The devices are so arranged that on the energizing of relay HI the earth potential is connected up over the very high resistance Wi5 to the b-lead of the connecting line so that the condenser associated with the bell of the subscribers station TStZ can gradually discharge'while the direct connection of earth over contact I'IrI on the release of relay RI does not take place until the discharge of the condenser has already proceeded so far that it is no longer possible for the bell in the second subscribers station to respond. This arrangement.

is particularly important since a removal of the receiver at the second subscribers station, occasioned by a brief operation of the bell, would produce undesirable disturbances in the establishment of the first subscribers call.

Devices are provided at the switching over point UStZ which prevent incoming exchange calls from seizing the two-party line when one of the subscribers is engaged in a call. Thus, for example, when the subscriber at station TStZ is engagedin a call contact 281*2 is closed as aresult of the energizing of relay R2 and accordingly the high resistance winding I of relay TI is short-circuited, while when the subscriber of station TStI is engaged in a call contact 2112 is closed on account of the energizing of relay TI and this similarly short-circuits the high resistance winding I of relay TI. In either case seizure of the line after testing on the c-lead, which is connected to earth over the low resistance winding II of relay TI, is not possible.

According to the second embodiment, Fig. 2, the controlling means (TI and T2) at the switching over point UStZ, are not energized in a circuit which is in effect when the system is at normal as is the case in Fig. 1, but are first operated when a call is initiated. The switching operations which take place in Fig. 2 are as follows: When the subscriber at station TStI, for example, takes up his receiver the following circuit is complete'd: earth, battery, winding I of relay RI, contacts ItI, 2t2, a-lead of the connecting line VL, winding I of relay UI, contact 3u2, line to station TStI, contact 4112, winding II of relay UI, contact 5ul, earth. In this circuit relay RI energizes but not relay UI. The former relay switches over its contacts thus connecting potential over resistance WiI and contact IirI to the pre-selector VWI by way of the b -lead. The following circuit is therefore set up for relay R in the pre-selector: earth, relay R, contact It,

b-lead contact BrI, resistance Wi I, battery, earth. The pro-selector is set in operation. At contact Brl a circuit is prepared for the high resistance winding I of relay TI.

When the pre-selector VWI tests on a free group selector relay T in the pre-selector energizes in the known manner over the c-lead and brings the pre-selector to rest. Contacts 913. and

Illt at the pre-selector are closed. A circuit is.

accordingly set up for relay TI at the switching over point USt2: earth, battery, relay A in the group selector, a-lead, contact 915, a-lead, contact BTI, winding I of relay TI, earth. Relay TI energizes and establishes a locking circuit over contact IItI: earth, battery, winding II of relay TI, resistance Wz'3, contact IItI, earth. At the same time contacts I2t| and ItI are opened and contacts I3tI and I4tl closed. The potential of the group selector is accordingly connected to the switching over point UStI by way of the a-lead of the connecting line so that relay UI energizes over the circuit: earth, battery, relay A in the group selector, a-lead, contact 915, a-lead, contacts I3tI, 2t2, a-lead of the connecting line, winding I of relay UI, contact 3111, line to sta tion TStI, contact 4102, winding II of relay UI, contact 5uI, earth. Relay UI operates and closes contact I5ul. At the same time both leads of the second subscribers station are disconnected by the opening of contacts IBuI and Hal. After the closing of contact I5ul relay UI holds up over: earth, contact IBTI, resistance Wi4, contact MtI, b-lead of the connecting line, contact l5uI.

The energizing of relay TI at the switching over point UStZ also has the effect of disconnecting relay RI. This relay, however, makes a delayed release on account of its short-circuiting winding II so that a certain period elapses before contact Brl opens. This period is sufiiciently long to ensure the energizing of relay UI at the switching over point UStI and the switching through of the b-lead of the connecting line. When contact I91I closes, relay RI having completely released, the loop to the group selector is securely closed at the switching over point USItI so that the false toll knock down signal (relay A energized, relay B deenergized) cannot be given in the group selector. Furthermore, through the release of relay RI winding I of relay TI is disconnected from the d -l'ead and resistance WM from the b-lead by the opening of contacts 811 and IIlrI, respectively. Relay TI holds up, however, throughout the duration of the call in a local circuit over its winding II. Relay TI thus serves to prevent incoming calls seizing the twoparty line when the latter is engaged.

On the release of the connection relay TI releases sinc when the pre-selector returns to normal the locking winding of relay TI is connected inparallel to relay T of the pre-selector. Relay TI therefore deenergizes, and closes contacts lit-I and. lZtI so that the system is once more restored to normal.

In the third modification and embodiment of the invention as shown in Fig. 3, the preselecting switches of the exchange devices are constructed as call finders, and this involves certain alterations and simplifications (at the switch-over point USt2) as compared with the arrangement employing preselectors as shown in the first two embodiments.

The switching operations of Fig. 3 are as follows: When, for example, the subscriber at station TStI takes up his receiver relay RI energizes atthe switch-over point UStZ in the following circuit: earth, battery, relay RI, contacts Itl, 2t2, a-lead of the connecting line VL, relay UI, winding I, contact 3u2, line to subscribers station TStI, contact 4u2, winding II of relay UI, contact 5ul, earth. Relay Ul does not energize in series with relay RI. Relay RI, however, energizes and closes its contacts. Resistance Wii is connected to the b-lead of the line to the call finder over contact ISrI while over contact lIrI the starting impulse is given to the call finder over the a-lead of the speaking line: earth, battery, relay R winding I in the call finder, contact 9t, a-lead, contact Bitl at the switch-over point UStZ, resistance Wi2, contact 'IrI, earth. Relay R energizes and causes the call finder to step round in the known way. The testing circuit for relay T in the call finder is prepared over the contacts lflr and Hi". When the call finder tests on the calling line relay T energizes, brings the call finder to rest in the known way and closes contacts I31? and Mt, so that now the potentials which are connected to the speaking line in the group selector which has been seized are connected to the two leads of the speaking line leading from the call finder to the switching over point USt2.

When the call finder tests on the calling line, relay TI is connected in parallel to the low resistance connected to the c-lead of the callfinder so that it can no longer remain energized. Relay TI accordingly releases, opens contact ItI and closes contact I 5H so that the a-lead of the speaking line is switched through to the calling station. Relay UI at the switching over point I UStI thereupon energizes: earth, contact 51L! winding II of relay UI, contact 411.2, line to the subscribers station TStI, contact 3u2, relay U winding I, a-lead of the connecting line, con tact 2152, NIH, a-lead of the speaking line passing over the call finder ASI to the group selector, battery, and earth. Relay III by closing contact I6ul causes the b-lead to be switched through, at the switching over point UStI. Relay UI thereupon holds up, after the disconnection of the earth at the switching over point UStI, over the b-lead of the connecting line, contacts I'li'i, I8rl, resistance Wi3, earth (at the switchingover point U St2). On account of the opening of contact Itl when the call finder tests on the calling line, the circuit for relay RI was broken. This relay makes a delayed release on account of its short-circuiting winding, so that the contacts 6r! and i811 only-open after acertain lapse of time. This interval is suilicient to enable relay U! at the switch-over point UStl to energize fully and for the switching through of the b-lead of the speaking line to occur at the switching-over point. When then on the release of relay RI contact its! is closed the loop between the speaking leads of the connecting path set up to the group selector is completed. Accordingly the disturbances which may occur if relay A in the group selector is energized over the a lead of the connecting line while relay B is not yet energized over the b-lead of the connecting line are avoided. These switching conditions of the two relays in the group selector (A energized,

B de-energized form the criterion for toll knock down. The same signal would also be given if on the release of relay Tl both leads of the speaking line were immediately switched through at the switching over point UStZ since some time 'elapses before the loop is completed over contact I Gul after relay Ul has energized over the a-lead.

In the embodiment of Fig. 3 just as in the arrangement according to Fig, 1 a reversal of the current direction takes place over one of the leads of the connecting line. In this case, however,

alteration of the current in stages is not absolutely necessary since when using call finders the reversal of the current direction only takes place when the call finder has been set on the calling line. Reversal of the current direction, therefore, occurs practically simultaneously with the energizing of the relay Ul of the calling station so that the disconnection of the other subscriber takes place immediately and any possible removal of the receiver at this subscriber's station provoked by the short operation of the bell remains inoperative. It is, however, possible, of course, to arrange the reversal of the current in stages in this arrangement also. In addition, in Fig. 3 arrangements are provided at the switching over point USt2 which prevent incoming calls from testing on the two-party line when one of the subscribers of this line is already engaged. Thus, if for example, subscriber TStZ is speaking either relay R2 is energized and contact 201*2 is closed when a call is initiated or relay T2 is deenergized and contact 2| i2 is accordingly closed, i. e. in both cases the high resistance winding I of relay T! is short-circuited so that a final selector cannot be set on this line.

What is claimed is: I

1. In a telephone system, a plurality of telephone lines, a plurality of connecting switches, a common connecting line individual to said switches over which said telephone lines have access to said switches to extend connections therefrom to other lines, means responsive to a cail from one of said telephone lines for taking said common connecting line into use, associating the telephone line with either one of said switches and operating the associated switch to extend the connection from said line, and means for delaying the switching through of the telephone line to the connecting switch until after it is determined thatthe call is an incoming or an outgoing one.

2. In a telephone system, a plurality of telephone lines, a plurality of connecting switches, a common connecting line individual to said linesv and said switches over which said telephone lines have access to said switches, means responsive to a call from one of said telephone lines for taking,

said common connecting line into use to the exclusion of the other telephone line, associating the calling telephone line with either one of said switches and operating the associated switch to extend the connection from said telephone line, means for determining whether said call is an outgoing one or an incoming one, and means.

connected at a common point to a connecting.

line, connecting switches accessible to said connecting line, means responsive to a call from one of said telephones for taking said connecting line into use and for disconnecting the other of said telephones to prevent its taking said com mon line into use, means also responsive to said call for seizing one of said connecting switches to extend the call, means for determining whether said call is an incoming or an outgoing one, said means comprising the grounding of said calling line, and means for delaying the extension of said call through said switches until said ground has been disconnected from said calling line.

l. In a telephone system as claimed in claim 3, means individual to each telephone line for disconnecting the other telephone line from use while said first line is calling and also for determining whether the call is any incoming or an outgoing one, said means operative only when the calling line has been switched through by the connecting switch;

5. In a telephone system, a pair of telephone lines connected to a common line, a pair ,of switches one for each of said lines accessible to said common line, means responsive to a call from one of said lines for taking'said common line into use and for engaging said common line with one of said switches, means responsive to the extension of the call through said'switch for reversing the flow of current over said line, other means responsive to the extension of said call for disconnecting the other of said telephones from the use of said common line, and means responsive to the reversal of current flow over said common line for preventing the operation of the ringer of the other telephone before said telephone is disconnected from the common line.

6. In a telephone system-as claimed in claim 5, in which the reversal of current fiow at the common line connects a high resistance to ground from one side of the line in order to gradually discharge the condenser associated with the ringer of the said other line and prevent the operation of the ringer before the said line is disconnected.

7. In a telephone system, a plurality of telephone lines connected to a common line, a plurality of connecting switches to which said com.- mon line has access, switching means at the junction of said common line and said connecting switches, a line relay in each telephone'line controllingthe incoming and outgoing direction of calls on said telephone line and also controlling said junction switching means, means responsive to an outgoing call from one of said telephone lines for'operating the associated line relay over said common line to operate the junction switching means and connect the calling line .to one of said connecting switches, and means responsive to the extension of the call through the said con-I 7 necting switch for releasing said line relay from in circuit of said line.

8. In a telephone system, a pair of telephones connected to a common line, a pair of connecting switches accessible to said line, a switching relay at the junction of said common line and said switches, a line relay for each line, means responsive to a call from one line for operating its associated line relay to connect said calling line to one of said switches and to operate said switching relay to connect the common line to the calling line, means responsive to the extension of the calling line through the operated switch to re lease the line relay from the line, and means also responsive to the extension of the calling line for disconnecting the other telephone from the common line.

9. In a telephone system, as claimed in claim 7, a selector switch accessible to said connecting switches and selectable thereby to extend the calling line, and means controlled over the line by a selected idle selector switch for controlling the operation of the line relay in the calling line.

10. In a telephone system as claimed in claim '7, in which the line relay is provided with differentially arranged windings, one of which is energized to operate the relay responsive to an outgoing call to extend the call, while the other winding is energized to release the relay responsive to the extension of the call through the connecting switch.

11. In a telephone system as claimed in claim '7 in which the line relay is provided with difierentially arranged windings one of which is energized to operate the relay responsive to an outgoing call from the associated line, while the other winding is energized to release the relay responsive to the extension of the call through the connecting switch, and means on said relay respon- 40 sive to its release for disconnecting said second winding from the line.

12. In a telephone system, as claimed in claim 7, in which the line relay of the calling line is included in the connecting path to each connecting switch and operates the junction switching means to disconnect the line relay of the other telephone line, said switching means comprising a relay for determining the incoming or outgoing direction of the call.

13. In a telephone system, a common junction line, a pair of telephone lines branched from one end of said common line, a pair of junction lines branched from the other end of said common line, a selecting switch individual to each of the said junction lines and operable thereover, means in each junction line responsive to a call from one of said telephone lines for extending the call over said common line to one of the junction lines to the associated selecting switch, and means responsive to the extension of the call for disconnecting the other of said junction lines from the common line and for disconnecting the other of said telephone lines from the common line.

14. In a telephone system, a common junction line, a pair of telephone lines branched from one end of said common junction line, a pair of junction lines branched from the other end of said common line, a selecting switch in which each of said junction lines terminate, means in each junction line responsive to a call from one of said telephone lines for extending the call over said common line to one of the junction lines and its associated switch, a line relay for each telephone line, the line relay of one of said lines responsive to the extension of a call from said line for disconnecting the other telephone line from the common line, and a switching relay for each junction line responsive to a call from one line to disconnect the other junction line from the common line.

15. In a telephone system, a common junction line, a pair of telephone lines branched from one end of said telephone line, a pair of junction lines branched from the other end of said common line, a selecting switch in which each of said junction lines terminate, means in each junction line controlled over one side of the common line in response to a call from one of said telephone lines for extending the call over said common line to one of the junction lines to the associated selecting switch, means responsive to the extension of a call for disconnecting the other of said junction lines from the common line for disconnecting the other of said telephone lines from the common line, a call from the other line being initiated over the other side said common line to the other junction line and selecting switch, and means responsive to the extension of a. call for switching through both sides of the common line to the calling junction line.

FRITZ WOLF. 

